The field of art to which this invention is directed is modified thermoplastic copolyester elastomers.
Segmented thermoplastic copolyester elastomers, which contain recurring polymeric long chain ester units derived from phthalic acids and long chain glycols and short chain ester units derived from phthalic acids and short chain glycols, are described in such patents as U.S. Pat. Nos. 3,651,014, 3,763,109 and 4,355,155.
Segmented thermoplastic copolyester elastomers have been blended with other compositions to modify their properties for specific end use applications. For example, segmented thermoplastic copolyester elastomers have been blended with low molecular weight epoxides to improve the melt stability as disclosed in U.S. Pat. No. 3,723,568.
Segmented thermoplastic copolyester elastomers, as described in U.S. Pat. Nos. 3,963,801 and 4,010,222, have been blended with ethylene-acrylic acid copolymers to improve the melt strength and blow molding processability.
U.S. Pat. No. 4,247,427 discloses hot melt adhesive composition made from blends of segmented thermoplastic copolyesters and low molecular weight polymers.
Ethylene-ethyl acrylate copolymers are described in Modern Plastics Encyclopedia as being among the toughest and most flexible of the polyolefins. These copolymers are often blended with other polyolefins, e.g., low density polyethylene, to produce intermediate-modulus products having many of the best properties of both polymers.
High impact resistant polymer blends, as described in U.S. Pat. Nos. 3,578,729 and U.S. 3,591,659, are made from ethylene-acrylic acid ester copolymers in admixture with linear saturated polyesters.
In U.S. Pat. No. 3,937,757, molding compositions having improved tracking resistance are disclosed, such compositions being blends of polybutylene terephthalate and polyolefins, e.g., ethylene-ethyl acrylate copolymers.
Other patents which describe blends of ethylene-ethyl acrylate copolymer and polyalkylene terephthalates are U.S. Pat. Nos. 3,953,394 and 4,324,869.
Research and development efforts are constantly being directed to developing polymer blends which have improved properties and economic advantages.